AFAIK, the Tamron and Sigma lenses send false information (read: that the aperture is at f/5.6 when it's actually f/6.3)

Yes, I know...but Doug stated, in effect, that at lens apertures narrower than specificed for the AF system, i.e. f/5.6, the AF detetors cannot function at all, i.e. it's an optical limitation, as opposed to a firmware limitation. The fact that an f/6.3 lens can AF, as can an f/8 lens under certain conditions, with an f/5.6-sensitive sensor, suggests that it's a firmware limitation, and not an optical limitation.

Great Idea! Is there an possibility to do this with original canon lenses too?

I just returned from an wildlife-photographer meeting (birdwatching) and the whole group was disappointed by this new camera.Does anybody know (or has an rumor), what Canon wants to do with these persons that need the "working AF at least @ f=8 performance" , you just posted before? (soory for poor English, Its not my native language).

It's possible now with original Canon lenses, but it's not supported or condoned by Canon. You just put a small piece of ScotchÂ® tape over the first three pins (i.e. on the counterclockwise side) on the rear side of the teleconverter (the side that mounts to the camera).

CarebbianTraveler

Yes, I know...but Doug stated, in effect, that at lens apertures narrower than specificed for the AF system, i.e. f/5.6, the AF detetors cannot function at all, i.e. it's an optical limitation, as opposed to a firmware limitation. The fact that an f/6.3 lens can AF, as can an f/8 lens under certain conditions, with an f/5.6-sensitive sensor, suggests that it's a firmware limitation, and not an optical limitation.

Well, the pupils have a certain size, and at f/5.6, they're not shaded at all and the focus sensors get the full amount of light. But when you attach a slightly slower lens as f/6.3 they start to get shaded, but there's still light coming thru to the sensors. So it works worse in low-light conditions. As people report here, the pupils are nearly fully covered at f/8 depending on the lens. This is why it may still work with a lot of light.

Yes, I know...but Doug stated, in effect, that at lens apertures narrower than specificed for the AF system, i.e. f/5.6, the AF detetors cannot function at all, i.e. it's an optical limitation, as opposed to a firmware limitation. The fact that an f/6.3 lens can AF, as can an f/8 lens under certain conditions, with an f/5.6-sensitive sensor, suggests that it's a firmware limitation, and not an optical limitation.

Well, the pupils have a certain size, and at f/5.6, they're not shaded at all and the focus sensors get the full amount of light. But when you attach a slightly slower lens as f/6.3 they start to get shaded, but there's still light coming thru to the sensors. So it works worse in low-light conditions. As people report here, the pupils are nearly fully covered at f/8 depending on the lens. This is why it may still work with a lot of light.

And the body may in fact let the AF system (try to) work at a reported aperture of f/6.3. But not f/8

AFAIK, the Tamron and Sigma lenses send false information (read: that the aperture is at f/5.6 when it's actually f/6.3)

Yes, I know...but Doug stated, in effect, that at lens apertures narrower than specificed for the AF system, i.e. f/5.6, the AF detetors cannot function at all, i.e. it's an optical limitation, as opposed to a firmware limitation. The fact that an f/6.3 lens can AF, as can an f/8 lens under certain conditions, with an f/5.6-sensitive sensor, suggests that it's a firmware limitation, and not an optical limitation.

The fact that the camera will not allow the AF system to attempt to work below a certain aperture is a firmware limitation.

The fact that it will not work (or work well) below a certain aperture is a hardware (optical) limitation.

As others have pointed out, the latter is not "knife-edge". If we can force the camera to "let the AF work" at an aperture of, for example f/8 (for an "f/5.6" AF detector). it may work with some difficulty. At f/6.3 it will likely work "pretty well".